Iron in Pregnancy: Why Some Iron Supplements Can Affect Your Gut and What You Can Do About It

on Aug 01 2026

Iron is one of the most important nutrients during pregnancy, yet some forms of iron have been associated with causing digestive discomfort. This can make it challenging to take supplements consistently at a time when iron needs are elevated. Research shows that moderate daily doses of iron, taken consistently once a day in a well-tolerated form, can support nutritional needs during pregnancy with less digestive discomfort and metallic aftertaste than other iron forms, reducing the need for complicated dosing routines. Here’s what the research says.

If you have ever taken a prenatal supplement and found yourself dreading it, you are far from alone, and iron may be playing a role. The conventional iron found in most standard prenatal supplements has a reputation for causing digestive discomfort and leaving behind a metallic aftertaste that can linger long after the tablet has gone down.⁽¹ ⁾ For the up to 70% of Australian pregnant women already battling digestive discomfort in the first trimester, adding that on top can feel a lot to ask.⁽²⁾It is no surprise that so many women quietly give up on their supplement routine, or that a growing number of prenatal vitamin brands have simply removed iron from their formulas altogether.

But here is the thing: iron plays an important role in supporting nutritional needs during pregnancy, and its absence in supplementation may create a gap that can be difficult to fill through diet alone.⁽³⁾

This suggests that perhaps it’s not just the ingredient, but the dose and form that deserve attention.

Why Does Your Body Need Iron in Pregnancy?

Iron does a lot of heavy lifting during pregnancy. It supports your energy levels and plays an important role in your baby's development.⁽⁴⁾ And here is the scale of the challenge: your iron requirements jump from 18mg per day before pregnancy to 27mg per day during it; this increase occurs at a time when nausea and food aversions can already make eating well less manageable.^(5,6)

Research suggests that up to 70% of pregnant women do not meet their iron nutritional needs, with some Australian studies showing iron gaps above 90%.^(3,4) This is why international bodies, such as the World Health Organization (WHO), recommend daily iron supplementation alongside folic acid for all pregnant women, regardless of their iron levels at the start of pregnancy.⁽⁷⁾

So, Why Are So Many Newer Supplement Brands Quietly Dropping Iron From Their Products?

The reasoning usually sounds sensible: iron causes stomach upset, so leaving it out reduces side effects, and allows healthcare practitioners to prescribe iron separately if needed. But in practice, leaving iron out of a daily prenatal supplement, during a period when iron nutritional needs are increased and shortfalls are common, is solving one inconvenience while potentially creating a new one.

A large 2023 systematic review and meta-analysis, pooling data from multiple studies, found that iron supplementation in pregnant women with adequate iron status reduced the risk of poor iron nutritional outcomes at full term by approximately 50%, and supported healthy pregnancy outcomes.⁽⁸⁾

Overall, the nutritional case for iron in a prenatal supplement is well supported: iron needs rise across pregnancy, Australian women are frequently falling short of meeting those needs through food alone and daily iron supplementation has shown to support maternal and foetal health when taken at appropriate doses during pregnancy.^(3,4,5,6,8)

Not All Iron Is Created Equal

The type of iron in your prenatal supplement is also relevant.

Some forms of iron used in supplements have been associated with digestive discomfort, including nausea and constipation, which occurs due to unabsorbed iron remaining in the gut where it can cause irritation.⁽¹^,⁹⁾ During pregnancy, when many women are already experiencing digestive changes, these symptoms may make it more difficult to maintain a consistent supplement routine,⁽⁹^,¹⁰⁾ and a supplement is only as effective as your ability to take it.

Next-generation iron forms can help address this challenge. SunActive® Iron, a microencapsulated form of ferric pyrophosphate, has demonstrated bioavailability and tolerability in pregnancy-specific clinical trials, making it well-suited for use in prenatal nutrition.⁽¹¹⁾

It also addresses something that does not get nearly enough attention in pregnancy nutrition: taste. Many women experience heightened sensitivity to taste and smell during pregnancy, and the metallic taste associated with some iron supplements may become an additional barrier to daily use.⁽¹⁰^,¹¹^,¹²⁾By using an innovative, flavour-masking microencapsulation technology, SunActive® Iron addresses two of the biggest barriers to maintaining a daily supplement routine: tolerability and taste.

As with all supplementation in pregnancy, consult your healthcare practitioner to know if SunActive® Iron is suitable for your needs.

More Iron Does Not Always Mean Better Iron

Here is something worth knowing, and something that surprises a lot of women (and even some healthcare practitioners) when they hear it. In pregnancy, a higher iron dose does not automatically mean better support. when it comes to multinutrient supplementation.⁽⁵⁾

Research increasingly shows that lower elemental iron doses can provide adequate nutritional support as part of a multinutrient supplement routine, with the added benefit of reduced risk of side effects.⁽⁵⁾

This means that a moderate dose of well-delivered iron can support healthy iron levels in healthy women, reducing the need for separate or complicated iron supplementation routines.

What About Taking Iron Every Second Day?

You may have heard the recommendation that taking iron on alternate days, rather than daily, improves absorption and reduces side effects. It is based on genuine research, but the full story is worth understanding before you change your routine.

This advice is based on research into higher-dose conventional iron forms; typically ferrous sulphate at 60mg of elemental iron or above - doses that are typically reserved for those with medically assessed iron needs.⁽¹³⁾ The science behind it involves a hormone called hepcidin, which rises when you take at least 40mg iron, and can temporarily reduce how much your body absorbs for up to 24 hours. In theory; spacing iron doses every second day gives hepcidin time to drop, potentially improving absorption.⁽¹⁴⁾ However, here is what the latest evidence shows: A 2025 review of several clinical trials involving over 1,000 people found no meaningful difference in iron outcomes between daily and alternate-day dosing.⁽¹³⁾And when it came to side effects? Overall, there was no significant difference between the two approaches either. The one modest advantage alternate-day dosing showed was a small reduction in metallic taste, which says less about absorption and more about the unpleasant taste of iron.⁽¹³⁾Therefore, alternate-day dosing appears to be relevant for specific iron forms and doses rather than for all prenatal supplement routines.^(13,14) Given that keeping track of multiple doses while managing digestive discomfort, fatigue, and the mental load of early pregnancy, it can be helpful to consult your healthcare professional to confirm whether this approach is appropriate for you.

Why The Format of Your Supplement Matters Too

Choosing the right form and dose of iron is one piece of the puzzle. The format your supplement comes in is another.

Standard tablets and capsules have physical size limits that lead to difficult trade-offs when it comes to fitting in adequate doses and numbers of nutrients: increase the tablet size, add more tablets per serve, or reduce the range and dose of nutrients included. Each presents its challenges; large and/or multiple tablets are harder to swallow at the best of times, let alone on a stomach already navigating first-trimester nausea.⁽¹⁵⁾ And reducing the number of nutrients to fit a tablet or capsule seems counterintuitive during a time when women need the most comprehensive nutritional support.

Oral dissolving powder formats remove this ceiling. A single daily sachet can accommodate a comprehensive nutrient panel such as iron, vitamin C, magnesium, and a full suite of micronutrients, without the size constraints of compressed formats. And when that iron uses taste-masking microencapsulation technology, the metallic aftertaste that makes conventional iron (and some powders) difficult to take is addressed, as is the need for complicated dosing routines.

The bottom line is simple. A prenatal supplement that delivers iron in a well-tolerated form, at an appropriate dose, in a format that works with your body and your lifestyle, can support iron levels in the body throughout your pregnancy journey.

This information is provided for general nutritional education only and does not constitute medical advice. Please speak with your healthcare provider about your individual nutritional needs during pregnancy.

References

Nguyen M, Tadi P. Iron supplementation. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan– [updated 2023 Jul 3; cited 2026 Jul 23]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557376/
Tan A, Foran T, Henry A. Managing nausea and vomiting in pregnancy in a primary care setting. Aust Fam Physician. 2016;45(8):599–603. Available from: https://www.racgp.org.au/afp/2016/august/managing-nausea-and-vomiting-in-pregnancy-in-a-pri
Maneschi K, Geller T, Collins CE, Gordon A, Grech A. Maternal diet quality and nutrient intakes across preconception and pregnancy are not consistent with Australian guidelines: Results from the pilot BABY1000 study. Food Science & Nutrition. 2023 Jul;11(7):4113-23. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC10345671/
Clarke L, Froessler B, Tang C, King K, Ross B, Kidson-Gerber G, Dugan C, Townsend L, Uppal T, Baxter L, Cook S. Iron optimisation in pregnancy: a Haematology in Obstetric and Women's Health Collaborative consensus statement. Intern Med J. 2025;55(2):300–7. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC11817901/
Frayne J, Pinchon D. Anaemia in pregnancy. Aust J Gen Pract. 2019;48(3):125–9. Available from: https://www1.racgp.org.au/ajgp/2019/march/anaemia-in-pregnancy
National Health and Medical Research Council; Australian Government Department of Health and Aged Care. Nutrient Reference Values for Australia and New Zealand: Iron [Internet]. Canberra: NHMRC; 2006 [cited 2026 Jul 23]. Available from: https://www.eatforhealth.gov.au/nutrient-reference-values/nutrients/iron
World Health Organization. Daily iron and folic acid supplementation during pregnancy [Internet]. Geneva: WHO; 2024 [updated 2024 Jul 26; cited 2026 Jul 23]. Available from: https://www.who.int/tools/elena/interventions/daily-iron-pregnancy
Watt A, Eaton H, Eastwick-Jones K, Thomas ET, Plüddemann A. The benefits and harms of oral iron supplementation in non-anaemic pregnant women: a systematic review and meta-analysis. Fam Pract. 2025;42(1):cmae079. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC11747145/
Tolkien Z, Stecher L, Mander AP, Pereira DI, Powell JJ. Ferrous sulfate supplementation causes significant gastrointestinal side-effects in adults: a systematic review and meta-analysis. PloS one. 2015 Feb 20;10(2):e0117383. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC4336293/
Gereklioglu C, Asma S, Korur A, Erdogan F, Kut A. Medication adherence to oral iron therapy in patients with iron deficiency anemia. Pakistan journal of medical sciences. 2016 May;32(3):604. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC4928407/
Patki A, Jyothi GS, Thobbi V, Srivastav A, Ganu G, Shah AS. Efficacy and safety of emulsified microsomal ferric pyrophosphate vs ferrous ascorbate in pregnancy with iron-deficiency anaemia: a randomized, comparative study. Sci Rep. 2025;15(1):39671. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC12612138/
Sadeghi N, Farazdaghi H, Parandoosh P, Dehghani P, Khatibi M. Relationship between pregnancy and sense of taste. Rom J. 2021;125(2):312–7. Available from: https://www.revistamedicinamilitara.ro/wp-content/uploads/2022/05/Relationship-between-pregnancy-and-sense-of-taste.pdf
Dhanvijay AD, Patidar V, Singh J, Kumar S, Mudgal SK, Varikasuvu SR, et al. Efficacy of daily versus alternate day oral iron supplementation for management of anaemia among general population: a systematic review and meta-analysis. BMC Pharmacol Toxicol. 2025;26:152. doi: 10.1186/s40360-025-00984-2. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC12372323/
Stoffel NU, von Siebenthal HK, Moretti D, Zimmermann MB. Oral iron supplementation in iron-deficient women: How much and how often?. Molecular aspects of medicine. 2020 Oct 1;75:100865. Available from: https://www.sciencedirect.com/science/article/pii/S0098299720300364?via%3Dihub
Kabeya K, Satoh H, Hori S, Sawada Y. Experimental study on patient preferences regarding the shape and size of medical tablets and capsules using three-dimensionally printed plastic model formulations. Patient preference and adherence. 2021 Apr 28:863-70. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC8091592/

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